1. Field of the Invention
The present invention is directed to medical systems used for monitoring pressure while at the same time permitting drainage of bodily fluids, and more particularly to a system for monitoring intracranial pressure while allowing for the drainage of intracranial fluid.
The measurement of intracranial pressure (ICP) is increasingly used in the management of nuerological and nuerosurgical conditions. A high ICP can result in decreases in the level of consciousness, cerebal blood flow, and cerebal oxygenation. High ICP can also cause shifting of the brainstem, collapsing of the ventricles and, if unrelieved, brain death. Increased ICP occurs as a result of brain blood and cerebral spinal fluid being contained in a non-compliant structure called the cranial vault. An increase in one of these components causes a direct decrease in the other components to compensate.
ICP monitoring enables medical personnel to take life saving measures to counteract or decrease ICP before permanent damage can occur. ICP monitoring is achieved through a specially designed pressure tubing used to connect a pressure transducer to an intracranial access. Intracranial accesses include the intra-ventricular catheter, the subdural catheter, and the epidural catheter. The pressure tubing typically provides some means for allowing for the drainage of fluids.
An example of an external ventricular drainage assembly is disclosed in U.S. Pat. No. 4,500,311 to Redmond et al. The disclosed drainage assembly is used in conjunction with a ventricular drainage catheter. A valve is connected to the catheter for selectively opening and closing the external ventricular drainage assembly to fluid flow. The valve can also be used for connecting a transducer to the system. An adapter is connected to the valve for providing access to the fluid flow path. A one-way valve is connected to this adaptor. A length of flexible tubing is connected between the one-way valve and a drip chamber. The drip chamber is in communication with a collection reservoir.
Such a system places the collection reservoir beyond, or downstream, of the pressure sensor. It is known that the fluid drained from the brain may be contaminated with blood cells, brain tissue, or other matter. These materials may cause the pressure transducer to provide inaccurate readings. Such inaccurate readings can be extremely dangerous to the patient in that corrective action may be taken when none is necessary, or the need for corrective action not recognized.
There are other types of drainage systems, some of which provide for drainage before, or upstream, of the pressure transducer. For example, see pages 24 and 25 of the Nursing Photobook entitled "Using Monitors" (1981). When a system of the type using a subarachnoid screw is used, the collection reservoir is often placed too close to the patient thus increasing the risk of meningitis.
In prior art systems such as the system disclosed in U.S. Pat. No. 4,500,311, it is necessary for a nurse to physically open a valve to allow drainage to occur. Such manual manipulation is time consuming and allows for human error if the stop cocks are not returned to the proper position.
Other problems which have been encountered with various types of ICP monitoring systems include: Tubing connection points are often not secure and, should they come apart, rapid decompression of the brain results. When the tubing comes apart, it provides an opportunity for contamination of the system which ultimately contaminates the brain and it may allow for an influx of air which may result in an air emboli or pnuemocephalus.
It is often not known how much fluid has been removed.
There is no provision of a means for securely stabilizing the drainage unit at a prescribed gradient, or for preventing the unit from being accidentally dropped to the floor causing rapid decompression or from being raised above the balance level causing back flow of the contents into the brain, resulting in a higher ICP and contamination.
There is no provision of a means for irrigation, balancing, administering drugs, and the dwelling of medications without breaking the system or risking backflow into the brain.
With some systems there is no ability to determine the amount of fluid removed at any given interval. This results in the inability to trend patents or determine the need for continued ICP monitoring and/or venting or the need to incorporate additional aggressive measures.
Some systems do not provide for the collection of specimens or cultures without breaking the sterility of the system.
Most systems must be changed every twenty four hours to prevent infection. With each system change, there is the possibility of human error and/or contamination of the patient.
In view of the shortcomings of the ICP systems of the prior art, it is desirable to provide an Intracranial Monitoring System capable of providing the above-identified features while at the same time insuring that the pressure readings are as accurate as possible.